The inventors previously proposed a refrigeration cycle, as shown in FIG. 1A, configured by a plurality of evaporators 8, 9 connected in parallel. In the configuration of FIG. 1A, a first pressure reducer 4 reducing the pressure of the refrigerant flowing into a first evaporator 8 among a plurality of evaporators 8, 9 is configured by a temperature type valve mechanism.
Further, by controlling the opening degree of the first pressure reducer 4 based on the refrigerant temperature of the radiator outlet sensed by a temperature sensing part 4a, the outlet refrigerant pressure of the radiator 2 is controlled to become a target pressure determined by the radiator outlet refrigerant temperature so as to improve the cycle operating efficiency. An accumulator 6 is arranged at the outlet side of the first evaporator 8 to prevent liquid refrigerant from being sucked into the compressor 1 from the channel at the first evaporator 8 side.
Further, a second pressure reducer 5 provided in parallel with the first pressure reducer 4 is configured by a temperature type expansion valve. This temperature type expansion valve is designed to reduce the pressure of the refrigerant flowing into the second evaporator 9. This temperature type expansion valve has a temperature sensing part 5a changing in internal pressure in accordance with the outlet refrigerant temperature of the second evaporator 9 and controls overheating of the outlet refrigerant of the second evaporator 9. Due to this, the liquid refrigerant is prevented from being sucked into the compressor 1 from the channel at the second evaporator 9 side.
Further, a solenoid valve 7 forming a shutoff valve for cutting off the flow of refrigerant of a second refrigerant channel B is provided in the second refrigerant channel B. Note that the first evaporator is for generating driver's seat side (front seat side) cooling air, while the second evaporator is for generating rear seat side cooling air.
Specifically, a solenoid valve 7 is provided in the second refrigerant channel B at the inlet side of the second pressure reducer 5. When cooling action of the second evaporator 9 is unnecessary, that is, when the operation of the rear seat side air-conditioning unit is stopped, the solenoid valve 7 is closed to cut off the flow of refrigerant of the second refrigerant channel B. Note that the solenoid valve 7 may also be provided at the outlet side of the second pressure reducer 5.
Further, in FIG 1A, the second pressure reducer 5 and the solenoid valve 7 are illustrated as being separate parts, but as disclosed in Japanese Patent Publication (A) No. 11-182983, they may also be integrally formed. On the other hand, when making the second pressure reducer 5 a fixed aperture type, it is possible to integrally form an orifice forming an aperture passage in the refrigerant channel in the housing (not shown) of the solenoid valve 7. Due to this, the second pressure reducer 5 can be formed integrally with the solenoid valve 7.
The configuration of FIG. 1A is proposed in Japanese Patent Application No. 2004-372956.
In such a refrigeration cycle, when turning on the switch for switching to the rear seat cooling operation so as to start the rear seat cooling operation during the cooling operation at the driver's seat side, a “whoosh” like unpleasant noise is caused. That is, this is the sound caused by the solenoid valve 7 opening when starting the second evaporator during operation of the first evaporator. When turning the switch on, if the solenoid valve 7 is opened, the large differential pressure between the refrigerant inlet pressure and refrigerant outlet pressure of the solenoid valve causes refrigerant to rapidly jet out from the valve opening part. The unpleasant noise is the rushing noise caused by this shock. This unpleasant noise gives the passengers an unpleasant or uneasy feeling.
Conversely, unpleasant noise is caused even when turning off the rear seat cooling operation switch during the cooling operation at both the driver's seat side and rear seat side. This is due to the reverse principle from the above. If the solenoid valve 7 is rapidly closed, the high pressure inlet refrigerant of the solenoid valve will rapidly be cut off. The unpleasant noise is the water hammer noise caused by this shock.